The present invention relates to a method of preparing a ready-to-use catheter, a catheter assembly for use in said method, and a ready-to-use catheter obtained by said method.
Urinary catheters having exterior coatings have been known for many years. Typically the coating is a hydrophilic layer designed to reduce the coefficient of friction in the wet condition, so that the catheter may be inserted relatively painlessly into the urethra of the patient, and likewise removed therefrom when required.
In one type of catheters having exterior coatings the wetting fluid is initially kept separate from the hydrophilic surface, and released immediately prior to use, thereby activating the hydrophilic surface. In another type of such products, the wetting fluid is arranged in such a way that the hydrophilic surface is maintained constantly wetted, and thereby ready for immediate use.
Catherisation means greater risk for infection in the urinary tract, and the increase in multi-drug resistant organisms, combined with the well-documented costs of treating healthcare-associated infections, has led to a strong mandate to address and eliminate all potential avenues for infection.
To reduce risk of infection, the urinary catheter as well as the wetting fluid needs to be sterilised. Furthermore, the surface of the urinary catheter should preferably remain uncontaminated prior to use.
Sterilisation of medical devices is typically performed at the time of manufacture, using techniques well known in the art such as beta-irradiation or fumigation with ethylene oxide gas.
However, sterilization of a wetted catheters e.g. an intermittent urinary catheter with a hydrophilic coating, is in general regarded cumbersome if not impossible, using the conventional techniques.
If gas, e.g. ethylene oxide, is used it must be allowed to have access to the catheter surface. However, the large volumes of wetting fluid surrounding the catheter will act as a barrier, preventing efficient penetration of ethylene oxide though the fluid. This means that the manufacturing process is made more complicated than would be desirable, requiring long and expensive periods of fumigation, and wet-sterilisation with fumigation is therefore generally regarded impossible
Sterilisation using irradiation of coatings in the activated state, has the well-known problem that an undesirable cross-linking of said coating occurs, removing the coatings abilities to retain water. This has the consequence that the coefficient of friction increases undesirable when the catheter is stored in the wet, i.e. activated state.
One way of overcoming this problem is known from EP2303346, which discloses that by adding one or more buffers to the wetting fluids, it will be possible to prevent the pH-value of the activated hydrophilic coating dropping to levels that promote acid formation during wet sterilization and subsequent storage, thereby preventing ruining the coating on the catheters.
Another way of overcoming said disadvantages, is disclosed in EP1131112, describing that the water retention can increase dramatically and consequently the initial coefficient of friction be kept low, by carrying out wet-sterilisation of a medical device if the aqueous solution comprises hydrophilic polymers. According to EP1131112, wetting a hydrophilic coating with a polymer solution protects the above-mentioned properties during exposure to sterilisation using radiation.
However, for catheters which are sterilised wet, the coating of the catheter will either lose its water retention ability or obtain an undesirable increase in the coefficient of friction, unless specific compounds, such as buffers or polymers, are added to the wetting fluid, or unless other specific requirements are met, making the manufacturing process expensive and complicated.
Another problem is that the hydrophilic coatings of catheters, which are sterilised and stored wet, tend to lose their water retention abilities, resulting in increases in the coefficient of friction. Thus, the effective life of the catheters are limited or even over by the time the catheter is utilized.
The above problems are the main reason why catheters conventionally are sterilised in a dry condition, and why the wetting fluid is kept separate from the hydrophilic surface, and released immediately prior to use, as disclosed e.g. in EP0923398, EP1958656, US2003/0055403 and EP2545952.
The provision of the wetting fluid in a catheter assembly as disclosed in e.g. EP0923398 entails many advantages. For example, there is no need to find a water supply, and catheterisation can constantly be performed in any location and at any time. Further, the entire activation/wetting process can be performed under sterile conditions, without opening of the package.
However, a drawback with the catheters requiring activation/wetting immediately before use is that the methods of wetting are relatively complicated, making the wetting process tedious and difficult to perform by e.g. disabled users, such as tetraplegics or sclerosis patients having poor dexterity.
Further, there is a significant risk that an inadequate wetting would occur from time to time, which would be both painful and potentially harmful for the user. Furthermore, in order to ensure a proper wetting, a substantial amount of wetting fluid is required, and in most products of this type, the wetting fluid in itself forms a substantial part of the overall weight of the product, making logistics more complicated and expensive.
In order to solve this problem, a vapour hydrated catheter assembly has been suggested in EP2060296. However, activation of the catheters coating using vapour, can result in inadequate wetting of the coating, which as discussed above will be both painful and harmful for the user. Furthermore, since only vapour is used for activating the catheter's coating in EP 2060296 the catheter assembly is a very complex construction and accordingly expensive to manufacture.
Thus, there is a requirement for providing a ready-to-use catheter in which the wetting fluid does not comprise expensive and complicated components in order to ensure that the coating can be maintained for a sustained period, where inadequate activation of the coating is prevented, and where the overall weight and size of the final catheter product is reduced more than hitherto known.